Release and arming mechanisms for ordnance devices are well known in the art. For obvious safety reasons, ordnance devices are carried on aircraft in an unarmed or non-explosive condition, subject to being armed after release to provide an armed or live ordnance device. When an ordnance device is released from a bomb rack or otherwise ejected or launched, it remains in a "safe" condition in which it will not detonate unless an arming wire connecting the ordnance device to the aircraft is held by a sufficient force to arm the ordnance device.
The arming wire is typically attached to the aircraft or other carrier by an arming mechanism, which, in its normal non-energized state, holds the arming wire against the forces of gravity, acceleration and wind, but releases the arming wire at a tension insufficient to arm the ordnance device. When electrically energized, however, the arming mechanism secures the arming wire in a non-releasable manner so that the ordnance device can be launched in an armed condition. The arming mechanism ensures that any ordnance device unintentionally launched will remain in a safe condition and permits the ordnance device to be intentionally launched in a safe condition, as when it is desired to unload ordnance devices prior to a landing.
According to most military specifications, a typical arming mechanism in an unenergized condition should retain the arming wire up to a predetermined force of 10 to 14 pounds. This retention force was considered to be sufficient to retain the arming wire until the ordnance device was released from the aircraft. After release, the weight of the ordnance device was then considered sufficient to overcome the retention force, pulling the arming wire from the arming mechanism and maintaining the ordnance device in an unarmed condition. It is now known, however, that under some dynamic loading conditions the specified 10 to 14 pound static retention force increases significantly, preventing the arming wire from pulling loose from the arming mechanism. Much of the inadvertent arming of ordnance systems or weaponry has occurred because of the occurrence of these loading conditions.
To overcome this problem, zero retention force mechanisms have been developed to insure that the unenergized arming mechanism will release the arming wire after the ordnance device is launched. One such device is shown and described in U.S. Pat. No. 4,266,462 issued to Carter et al. Such prior devices, however, require major redesign to the delivery system and can be relatively expensive. Furthermore, these special devices and delivery systems are not interchangeable in all applications with old ordnance delivery systems, which have been in the field for many years. For example, no suitable zero retention force mechanisms have been developed for jaw-, ball- or cone-type release and arming mechanisms.
It should, therefore, be appreciated that there is still a need for an improved release and arming mechanism that enables field replacement on many old jaw-, ball- or cone-type ordnance delivery systems while updating the delivery system with a zero retention force or low retention force capability. Such a mechanism should also increase system reliability and should prevent any catastrophic failure. The present invention satisfies this need.